Software defined network (SDN) technology may provide a framework for network communications, and realize centralized control and distributed forwarding for network devices. As to the SDN technology, its network functionality may be divided into two parts, i.e., controllers and datapaths, which may interact with each other via a secure channel. The controller may offer a central management for the network devices (such as virtual machines) under its control, and regulate the forwarding of the datapaths.
There are various different types of implementation for the SDN technology, and OpenFlow technology is an example of them. The OpenFlow technology may expand the packet forwarding based on Media Access Control (MAC) and the route forwarding based on Internet Protocol (IP) to the flow forwarding described by multiple fields of a packet header. In the meantime, the OpenFlow technology may decouple a control plane from forwarding devices, and transfer a role of decision making for forwarding from a forwarding device (such as a switch) to a centralized controller.